For purposes of the present description, a “shade” type of window covering is a type of area goods or panel whose final form is either (1) a single, continuous, integral piece of flexible fabric, without seams or joints in the fabric, as exemplified by the common roller shade, or (2) a series of identical or very similar strips of flexible fabric, directly contacting and connected to adjacent such strips by gluing, stitching, ultrasonic welding or the like, as exemplified by certain commercially available cellular honeycomb shades. In contrast, and also for present purposes, a “blind” is neither a type of area goods nor a panel, but instead comprises a series of separate, usually substantially rigid and opaque, elements (often called “slats” or “vanes”) that are connected to one or more articulating members that permit the elements to be tilted through varying degrees of inclination to control the amount of light and visibility through the blind. Unlike a “shade,” the elements of a “blind” are not directly joined (such as edge-to-edge) to the adjacent element in the series.
A third type of product, a “fabric-vane window shading,” combines some of the physical characteristics of both a shade and a blind. An example of such a product is shown in Corey, U.S. Pat. No. 6,024,819, wherein the product is described as a “fabric Venetian blind.” The vanes may be formed of a relatively opaque fabric, rather than a rigid material as in the case of a conventional Venetian blind, and are interconnected by full-area front and rear panels of a sheer or relatively translucent material. Thus, the resulting product is in the form of a panel comprising multiple stacked expandable cells, each of which is defined by upper and lower vanes and a portion of each of the front and rear panels. In that sense, a “fabric-vane window shading” constitutes a “shade” rather than a “blind” under the definitions used herein. It will therefore be referred to as a “fabric-vane window shading” in the present patent application.
Also, as used herein, “preform” refers to an elongated strip-like element or constituent part of a shade panel, which element may be flat or folded, single or multiple-piece, which has been cut to final (or final but for minor trimming) length for use in a window covering fabricated to fit a window of a particular size. This preform, or intermediary product, when joined directly along its longitudinal edges to identical or substantially identical adjacent preforms in a stack of such preforms, forms the panel portion of a window covering.
In the various embodiments disclosed herein, the preforms are typically described as having a “length” corresponding to the “width” of the window for which the completed window covering is ordered, because the preforms will be most commonly be oriented horizontally when installed in such window. Also, for the same reason, it is contemplated that the accumulation step where successive preforms are placed in side-by-side adjacency for compression and bonding, will usually be in a vertical “stack.” However, it is to be understood that the process disclosed herein could also be used for making window coverings having vertically oriented elements or preforms, where the “length” of the preform will be oriented vertically, parallel to the “height” dimension of the window to be covered. Similarly, the “stacking” step could be implemented by bringing successive preforms into horizontal or inclined, rather than vertical, adjacency.
In all cases discussed herein, the fabric panel portion of the window covering is suitable for, and intended to be assembled to, appropriate hardware, such as top and bottom rails, control cords or wands, and the like, to facilitate installation and operation.
A popular type of window covering is a cellular window shade, made from either individual folded strips bonded to adjacent strips or a continuous transversely folded sheet of flexible web (fabric or film). The fold lines are set by a thermal curing process, and a stack of the folded strips or sheet is then bonded along adjacent parallel bond lines to create an expandable honeycomb structure in the form of a continuous column of joined cells.
U.S. Pat. Nos. 4,450,027 and 4,603,072 to Colson describe one method of forming a “single-cell” honeycomb window covering, i.e., a product having a single column of joined expandable cells. According to that method, a continuous narrow strip of longitudinally moving flexible material is progressively folded into a flat, generally C- or U-shaped tube and then thermally treated to set the folds, while maintaining tension in the tube. Longitudinal lines of adhesive are then applied to the moving tube, and the tube is spirally wound onto a rotating frame having elongated flat portions, thereby creating a stack of cells of single-cell width that are adhered to each other by the previously applied adhesive. Straight sections of this bonded stack are then severed from the remainder of the wound tubing. This method is time-consuming and expensive, and generates non-flat portions of the winding that connect the adjacent flat portions of the rotating frame and that must be scrapped. The resulting bolt of expandable single-cell honeycomb fabric may be 12 or more feet wide and 40 feet long in its fully expanded condition. These bolts are then placed in inventory until needed to fill a customer order. In response to a specific customer-ordered window width and height, a stocked oversize bolt or panel of the ordered color and pattern is cut down to the required width and number of cells to provide the drop length needed for the height of the ordered windows, requiring skilled labor and inevitably resulting in substantial waste even if the remaining portion of a given bolt is returned to the inventory. Because future ordered window sizes cannot be predicted, except in a statistical way, operators must use complex and imperfect algorithms to minimize the residual waste as individual window-size sections are cut from the stocked blocks. Typical waste factors in converting blocks to window-size sections range from 25% in smaller shops to 15% in large-volume fabricators with steadier order streams.
A similar method is disclosed in Anderson, U.S. Pat. No. 4,631,217, where the initially folded and creased material has a Z-shaped cross-section, with each winding of such strip forming the front of one cell and the rear of an adjacent cell after stacking and bonding.
A later-developed method of forming expandable honeycomb fabric is disclosed in commonly-assigned U.S. Pat. No. 5,193,601 to Corey et al. That method involves continuously feeding a broad web of flexible material, having a width that is at least as wide as the required width of the window covering, through a web-treating stage where desired coloring or patterning are printed onto the material. The web is then fed through appropriate drying or curing zones, and then between printing rollers that apply transverse parallel lines of adhesive at predetermined longitudinally spaced locations on the moving web. The web then passes through a station that partially cures the lines of adhesive to an intermediate, handleable state. The web next passes through a creasing and pleating apparatus that forms transverse fold lines at predetermined intervals and predetermined locations relative to the adhesive lines. A predetermined length of the web, now folded into a creased and generally serpentine shape, is then severed from the upstream portion of the web and collected and compressed into a stack, where the adhesive is further cured to permanently bond adjacent folds in a predetermined cellular pattern of double-cell width. This double-cell product can also be used to make single-cell panels by simply cutting off one of the columns (which, to reduce waste, is initially made narrower by shifting the adhesive line position), or by severing alternate internal ligaments between adjacent front and rear cells. While faster than Colson's method, this method requires containment of large stacks of material for curing, usually done thermally by heating the entire stack and its containment structure. That heating method consumes excessive energy and time, and carries a risk of thermal distortion of the stack.
The initial web is typically formed into large bolts in the form of columns of expandable cells, typically 10 ten feet wide and 40 feet in fully expanded length. As in the case of the single-cell product described above, the inventorying, subsequent cutting labor and scrapped material is costly.
Another method of forming a generally cellular type of product is disclosed in commonly-assigned Corey, U.S. Pat. No. 6,024,819. There, a fabric-vane window shading comprising sheer front and rear panels and relatively opaque fabric vanes is formed from an initial elongated, narrow, three-element strip having an opaque central portion secured by adhesive, stitching or other bonding technique along its two longitudinal edges to adjacent sheer strips. Of course, the three elements could be made from other materials, with the three components being the same or different. That three-element strip is then helically wound onto a supporting surface, with each successive winding only partially overlapping the immediately preceding winding (like slabs of bacon in a display pack) and bonded together along longitudinally extending bond lines. Finally, the resulting loop of layered material is cut open along a cutting line perpendicular to the longitudinally extending bond lines and then stored in rolls that may be 10 feet wide and 13-14 feet long if unrolled to the full drop-length of the deployed condition. As in the case of the other disclosed methods, the cutting down of the initially formed cellular product into smaller pieces for specifically sized window coverings requires skilled labor and results in substantial amounts of scrapped material.
There is a need for a more economical method of forming cellular window shades and other types of window treatments such as Roman-style shades and fabric-vane window shadings, each of which type of shade is (or could be) made from joined and repeating flexible elements. Specifically, it would be desirable to eliminate the need to initially form and stock broad panels or bolts of such formed goods in various colors and patterns, from which individual window coverings must later be cut to fill customer orders for window coverings of specified length and width, with inevitable scrapping of unusable left over material.